A Metropolitan police CO19 firearms unit officer has been taken off operational duty after losing a Taser stun handgun – with four cartridges – when he drove off with them on the roof of a police vehicle as he left a firearms base in Lambeth, south London, yesterday morning.

Police believed it may have fallen off before Vauxhall Cross, where he stopped for fuel.

Scotland Yard said the Directorate of Professional Standards had been told and an internal investigation was under way. Anyone with information about the Taser, made of bright yellow plastic, can call the Met on 0300 123 1212.